The architecture of the Circuit Switched (CS) and Packet Switched (PS) call establishment in Wideband Code Division Multiple Access (WCDMA) networks requires first that a Radio Resource Control (RRC) connection establishment between the User Equipment (UE) and the Radio Network Controller (RNC) as shown in FIG. 1. Typically this is done so that the UE is moved from an idle mode to a CELL_DCH state (Dedicated Channel, DCH). After this signaling exchange, the signaling between the UE and the CN (core network, PS or CS) can begin. This signaling is initiated by a service request message sent towards the PS CN (e.g., or a CM (Connection Management) service request message to the CS CN). The purpose of the Service Request procedure is to transfer the PMM (Packet Mobility Management) mode from a PMM-IDLE to a PMM-CONNECTED mode, and/or to assign a radio access bearer in the case that a Packet Data Protocol (PDP) context is activated without a radio access bearer being assigned. Reference in this regard can be had to 3GPP TS 24.008, 3rd Generation Partnership Project; Technical Specification Group Core Network; Mobile radio interface Layer 3 specification; Core network protocols; Stage 3 (Release 5).
If no PDP context is active, the UE continues with the PDP (Packet Data Protocol) context activation procedure to activate the PDP context (or setup for CS voice) as shown in FIG. 2.
It should be noted that as currently specified the service request is carried within the RRC: Initial Direct transfer and RANAP: Initial UE Message over Uu and Iu interfaces as transparent NAS-PDU (Non-Access Stratum-Packet Data Unit). The Uu interface is the interface between the UTRAN and the UE, while the Iu is the interconnection point between the RNC or a BSC (Base Station Controller) and 3G (Third Generation) core network (CN). RANAP (Radio Access Network Application Part) is the Radio Network Layer signaling protocol for the Iu interface (e.g., between the UTRAN and Core Network). The RANAP resides in the UTRAN and the Core Network (CN). FIG. 2 presents the logical signaling transfer.
As can be seen, since the RRC connection setup and service request are performed sequentially, the current specifications inherently containing the setup delay of each of these sequential procedures. It can be shown that the RRC connection setup delay can be approximately 500 milliseconds (ms) and the Service Request setup delay can be approximately 70 ms. If one includes PDP context activation of about 1200 ms, it can be appreciated that even if using more optimized signaling transfer, such as by utilizing High Speed Uplink Packet Access (HSUPA) and High Speed Downlink Packet Access (HSDPA) for the Signaling Radio Bearers (SRBs), since these procedures are performed in sequence, achieving further delay reductions are extremely difficult.
Recent observations from commercial WCDMA networks have shown that this sequence of different procedures can introduce an unacceptable amount of delay during CS and PS call establishment.
It is known that in the GSM (Global System for Mobile communication) CS, mobile-originated call establishment case, the service request message (CM SERVICE REQUEST) is sent piggy-backed, i.e., contained in the GSM Level 2 (L2) (LAPDm; Link Access Protocol on the D-Channel, modified) messages requesting the establishment of the L2 link (which in turn, after successfully established, creates a successful Radio Resource connection). For PS services, however, the situation is different, as for any signaling or link establishment between the MS and the network a TBF (temporary block flow) establishment procedure takes place. This establishment procedure itself does not carry any Layer 3 (L3) signaling or service request. The inventors have realized that the call establishment process for PS (and CS) services is not as efficient as the process could be.